As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
In many applications, one or multiple information handling servers may be installed within a single chassis, housing, enclosure, or rack. Communication between servers and/or between enclosures may often be accomplished via cables, and many communications standards and protocols employ a copper cable implementation for differential signaling. For example, a shielded dual axial differential pair cable 10, a cross section of which is shown in FIG. 1, is traditionally used for short to medium reach (e.g., less than 10-20 meters) in standards including, but not limited to, Serial Attached Small Computer System Interface (SAS), InfiniBand, Serial Advanced Technology Attachment (SATA), Peripheral Component Interconnect Express (PCIe), Double Speed Fibre Channel, Synchronous Optical Networking (SONET), Synchronous Digital Hierarchy (SDH), and 10 Gigabit Ethernet (10 GbE). As shown in FIG. 1, cable 10 may include two substantially parallel and substantially adjacent wires 12 each formed from an electrical conductor 14 (e.g., copper), surrounded throughout the length of conductor 14 by an electrical insulator 16 (e.g., plastic), an electrically grounded drain 18 comprising an electrical conductor (e.g., copper) running substantially parallel to and substantially adjacent to each of the wires, and an electrically grounded shield 20. Shield 20 may comprise foil of an electrical conductor (e.g., aluminum) wrapped around wires 12 and drain 18 in a helical fashion.
However, to ensure complete shielding by shield 20 in the presence of cable bending, shield 20 is typically wrapped with a significant amount of overlap. As a result of such overlap, the axial direction of shield 20 (e.g., parallel with the length of wires 12) will include a periodic impedance discontinuity. In such a cable 10, return current may be strongest at the lateral portions of cable 10 (e.g., on the left and right of cable 10 in the orientation shown in FIG. 1), while being weaker in other areas (e.g., on the left and right of cable 10 in the orientation shown in FIG. 1). Thus, a significant portion of the return current may flow through the periodic discontinuity of shield 20, potentially leading to resonance at an undesired frequency, thus likewise potentially leading to lower available signal bandwidth on the cable than would otherwise be available in absence of the resonance.
One solution to this problem has been to construct a cable 30 with a dual drain construction, a cross section of which is shown in FIG. 2. As shown in FIG. 2, each of two electrically-grounded drains 18 may be formed laterally to, substantially in parallel with, and substantially adjacent to, a respective wire 12. In such a construction, while some return current may flow on shield 20, the largest portion of such return current may flow through drains 18, thus avoiding the periodic impedance discontinuity of shield 20, and reducing the occurrence of undesired resonance. However, such a dual-drain cable 30 increases cable size (e.g., width) over a similar single-drain cable 10, which may not be suitable for applications in which a high volume of cables is required.
Another solution to the shield-induced resonance problem has been to construct a cable with a uniform shield. However, such solutions are often cost-prohibitive, as cost may exponentially increase as cable length increases.